Vlan, DHCP and moving computers problem

  • Thread starter Thread starter erman
  • Start date Start date
E

erman

Hello,
I don't know much about network, so sorry If I'm saying stupid things
:)
My friends want me to do a search about this problem.
In our company, the netwoek admin created some vlans based on
buildings and floors. And we are using DHCP. For exemple in the first
building the first floor's ip range is 172.17.0.1-172.17.7.254, the
second floor is 172.17.8.1-172.17.15.254.
For every floor the ip helper is defined. The subnet mask is
255.255.248.0 (for all floors). For the first floor the gateway is
172.17.0.1 for the second 172.17.8.1 etc..
When we move a computer from the first floor to the second floor,
there are many problems we encounter.
The main problem is that they don't get the ip from the DHCP server
directly. And we can't remove the computer from the domain it gets dns
lockup problem.
For 8 computers we've founs 3 different solutions.
1-For the 2 computers we've deleted their DNS records from the DNS
server (forward and reverse) after the release renew it worked out.
They got the second floor ip address
2-For the next computer it didn't work out. So we've reserved their ip
from the DHCP server (for second floor) (release-renew was OK).Then
we've deleted the reservation.(release-renew) and It got the second
floor ip address.
3-For the other none of the first 2 solutions worked out it was
getting the same old first floor ip address. When we delete the dns
records and dhcp records manually and release renew it was getting the
old first floor adrress also. Then we've uninstalled the network card.
After the reinstall it didn't get automatically an ip address from the
DHCP. After the release renew it got the second floor ip but with an
existing ip address error. But it's working now.
I don't know what to do. I don't know what may be the problem. I need
your help :)
Thank you
Erman Ulusoy
 
You need to check your configs, both on the DHCP server and on the router.
The DHCP Server should have 1 scope for each different subnet that you are
using. Verify that the options for each scope is correct ( Default Gateway
etc. ).

The IP Helper setting on the router should allow the DHCP broadcast to get
forwarded to the DHCP server. The DHCP Server hands out leases based on the
GIAddr field on Relayed DHCP Requests ( This is the Gateway's address for
that particular network segment ).

DNS shouldn't come into the picture when obtaining a new IP. And if you've
configured your DHCP server properly, when the IP is leased, the client and
/ or the DHCP Server will update the DNS database properly.

One last thought, if you don't release the address before you try to renew,
the NIC will try to unicast the DHCP Discovers to the DHCP server it
obtained its initial release. This should only be an issue if you move the
machine without powering it down.

You may want to sniff the network to see exactly what is going on.
 
erman said:
Hello Dusty thanks for your answer.
We are using 1 scope for each vlan but they are all under a
superscope. I've found in some of the newsgroups post that this could
Click to expand...

Superscopes are used to make multiple ranges behave as a single range. That
is not what it sounds like you want. Do not use Superscopes,...just use
*normal* individual Scopes for each "subnet".
 
We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.
 
We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.
 
That doesn't mean you should keep the Superscope. If you have more than one
subnet in the Superscope,...it is only a matter of time before one of the
clients gets an address from the wrong subnet and gets cut off on the
network.

Superscopes take everything listed in them and makes them act as one large
single scope. You need to think that through to its logical conclusion.
 
Hello phillip I'll tell this to our netw. admin.
Thank you for your reply. And I'll let you know the result.
Erman Ulusoy
 
Phillip is correct...
See:
http://www.microsoft.com/resources/...ddocs/en-us/sag_DHCP_imp_UsingSuperscopes.asp

Superscopes should only be used where: multiple logical IP networks exist
on a single physical segment.

In your case, when you set up the vLAN, this results in two physical
segments, since clients on one vLAN cannot ARP for clients on the other (nor
can they IP broadcast to the other vLAN)... Thus, the superscope should not
be used in this case.

--
==============================
Chris Edson
(e-mail address removed)

Upcoming Tech Chat !
August 24, 1:00-2:00p Pacific
DHCP: Configuring and Deploying DHCP with Windows Server 2003 Part 2
Join the DHCP test team as we talk about any questions, concerns, or
recommendations you might have for DHCP Server in Windows Server 2003.
Chat Room:
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http://www.microsoft.com/technet/community/chats/trans/network/net1120.mspx

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================


Phillip Windell said:
That doesn't mean you should keep the Superscope. If you have more than
one
subnet in the Superscope,...it is only a matter of time before one of the
clients gets an address from the wrong subnet and gets cut off on the
network.

Superscopes take everything listed in them and makes them act as one large
single scope. You need to think that through to its logical conclusion.


--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


erman said:
We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.

"Phillip Windell" <@.> wrote in message
Click to expand...
Click to expand...
 
Hello chris, helo phillip,
I've discussed with out network admin. And we think that you're right.
There is 1 question which remains in my mind. When I click on the link
sent by chris, I see 3 examples of superscope. In the 2nd example I
don't understand how the dhcp server decides which IP to give to one
of the member of the multinet. I mean how does it decides which
computer will have 192.168.1.2 or 192.168.2.2
Thank you
Erman Ulusoy

Chris Edson said:
Phillip is correct...
See:
http://www.microsoft.com/resources/...ddocs/en-us/sag_DHCP_imp_UsingSuperscopes.asp

Superscopes should only be used where: multiple logical IP networks exist
on a single physical segment.

In your case, when you set up the vLAN, this results in two physical
segments, since clients on one vLAN cannot ARP for clients on the other (nor
can they IP broadcast to the other vLAN)... Thus, the superscope should not
be used in this case.

--
==============================
Chris Edson
(e-mail address removed)

Upcoming Tech Chat !
August 24, 1:00-2:00p Pacific
DHCP: Configuring and Deploying DHCP with Windows Server 2003 Part 2
Join the DHCP test team as we talk about any questions, concerns, or
recommendations you might have for DHCP Server in Windows Server 2003.
Chat Room:
http://communities2.microsoft.com/home/chatroom.aspx?siteid=34000015

Transcript of previous chat:
http://www.microsoft.com/technet/community/chats/trans/network/net1120.mspx

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================


Phillip Windell said:
That doesn't mean you should keep the Superscope. If you have more than
one
subnet in the Superscope,...it is only a matter of time before one of the
clients gets an address from the wrong subnet and gets cut off on the
network.

Superscopes take everything listed in them and makes them act as one large
single scope. You need to think that through to its logical conclusion.


--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


erman said:
We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.

"Phillip Windell" <@.> wrote in message
Click to expand...
Hello Dusty thanks for your answer.
We are using 1 scope for each vlan but they are all under a
superscope. I've found in some of the newsgroups post that this could

Superscopes are used to make multiple ranges behave as a single range. That
is not what it sounds like you want. Do not use Superscopes,...just use
*normal* individual Scopes for each "subnet".
Click to expand...
Click to expand...
Click to expand...
 
I don't know and I don't trust it either. I never use Superscopes,...there
are too many other *good* ways to implement a network without using
superscopes. It is more dependable and solid to just create separate
segments in the first place (physical or logical VLANs) and be done with it.

When there are separate segments there is information provided by whatever
is being used as a Relay Agent so that the DHCP knows which scope to grant
an address from, so it is kinda a "no-brainer". When Superscopes are used on
a single segment, then I don't know how it knows which client is supposed to
get and address from which "subnet".

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


erman said:
Hello chris, helo phillip,
I've discussed with out network admin. And we think that you're right.
There is 1 question which remains in my mind. When I click on the link
sent by chris, I see 3 examples of superscope. In the 2nd example I
don't understand how the dhcp server decides which IP to give to one
of the member of the multinet. I mean how does it decides which
computer will have 192.168.1.2 or 192.168.2.2
Thank you
Erman Ulusoy

"Chris Edson [MSFT]" <[email protected]> wrote in message
Phillip is correct...
See:
http://www.microsoft.com/resources/...ddocs/en-us/sag_DHCP_imp_UsingSuperscopes.asp

Superscopes should only be used where: multiple logical IP networks exist
on a single physical segment.

In your case, when you set up the vLAN, this results in two physical
segments, since clients on one vLAN cannot ARP for clients on the other (nor
can they IP broadcast to the other vLAN)... Thus, the superscope should not
be used in this case.

--
==============================
Chris Edson
(e-mail address removed)

Upcoming Tech Chat !
August 24, 1:00-2:00p Pacific
DHCP: Configuring and Deploying DHCP with Windows Server 2003 Part 2
Join the DHCP test team as we talk about any questions, concerns, or
recommendations you might have for DHCP Server in Windows Server 2003.
Chat Room:
http://communities2.microsoft.com/home/chatroom.aspx?siteid=34000015

Transcript of previous chat:
http://www.microsoft.com/technet/community/chats/trans/network/net1120.mspx

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================


Phillip Windell said:
That doesn't mean you should keep the Superscope. If you have more than
one
subnet in the Superscope,...it is only a matter of time before one of the
clients gets an address from the wrong subnet and gets cut off on the
network.

Superscopes take everything listed in them and makes them act as one large
single scope. You need to think that through to its logical conclusion.


--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.

"Phillip Windell" <@.> wrote in message
Click to expand...
Hello Dusty thanks for your answer.
We are using 1 scope for each vlan but they are all under a
superscope. I've found in some of the newsgroups post that this could

Superscopes are used to make multiple ranges behave as a single
Click to expand...
range.
That
is not what it sounds like you want. Do not use Superscopes,...just use
*normal* individual Scopes for each "subnet".
Click to expand...
Click to expand...
Click to expand...
 
It picks the first available address in the multinet. Since they are
grouped together by a superscope (which tells the DHCP Server that both
subnets are combined into one, and should be treated as one entity), the
DHCP Server does not differentiate between the two member scopes.

-Chris

--
==============================
Chris Edson
(e-mail address removed)

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================

erman said:
Hello chris, helo phillip,
I've discussed with out network admin. And we think that you're right.
There is 1 question which remains in my mind. When I click on the link
sent by chris, I see 3 examples of superscope. In the 2nd example I
don't understand how the dhcp server decides which IP to give to one
of the member of the multinet. I mean how does it decides which
computer will have 192.168.1.2 or 192.168.2.2
Thank you
Erman Ulusoy

Chris Edson said:
Phillip is correct...
See:
http://www.microsoft.com/resources/...ddocs/en-us/sag_DHCP_imp_UsingSuperscopes.asp

Superscopes should only be used where: multiple logical IP networks
exist
on a single physical segment.

In your case, when you set up the vLAN, this results in two physical
segments, since clients on one vLAN cannot ARP for clients on the other
(nor
can they IP broadcast to the other vLAN)... Thus, the superscope should
not
be used in this case.

--
==============================
Chris Edson
(e-mail address removed)

Upcoming Tech Chat !
August 24, 1:00-2:00p Pacific
DHCP: Configuring and Deploying DHCP with Windows Server 2003 Part 2
Join the DHCP test team as we talk about any questions, concerns, or
recommendations you might have for DHCP Server in Windows Server 2003.
Chat Room:
http://communities2.microsoft.com/home/chatroom.aspx?siteid=34000015

Transcript of previous chat:
http://www.microsoft.com/technet/community/chats/trans/network/net1120.mspx

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================


Phillip Windell said:
That doesn't mean you should keep the Superscope. If you have more than
one
subnet in the Superscope,...it is only a matter of time before one of
the
clients gets an address from the wrong subnet and gets cut off on the
network.

Superscopes take everything listed in them and makes them act as one
large
single scope. You need to think that through to its logical conclusion.


--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.

"Phillip Windell" <@.> wrote in message
Click to expand...
Hello Dusty thanks for your answer.
We are using 1 scope for each vlan but they are all under a
superscope. I've found in some of the newsgroups post that this
could

Superscopes are used to make multiple ranges behave as a single
range. That
is not what it sounds like you want. Do not use Superscopes,...just
use
*normal* individual Scopes for each "subnet".
Click to expand...
Click to expand...
Click to expand...
 
Hello chris,
Thank you for your answer. Please correct me If I'm wrong
In this 2nd example of superscope it seems to be that the 192.168.1.11
computer won't be able to connect to other computers as the subnet
mask is 255.255.255.0
(the computers with 192.168.2 and 192.168.3) When I define 3 scopes
with 192.168.1 , 192.168.2 , 192.168.3 how the dhcp server decides
whic computer is in 192.168.1.* or 192.168.2.* or 192.168.3.*.
I mean isn't it a network with 3 groups of computers where neither of
the groups see the other one?
Thank you
Erman Ulusoy


Chris Edson said:
It picks the first available address in the multinet. Since they are
grouped together by a superscope (which tells the DHCP Server that both
subnets are combined into one, and should be treated as one entity), the
DHCP Server does not differentiate between the two member scopes.

-Chris

--
==============================
Chris Edson
(e-mail address removed)

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================

erman said:
Hello chris, helo phillip,
I've discussed with out network admin. And we think that you're right.
There is 1 question which remains in my mind. When I click on the link
sent by chris, I see 3 examples of superscope. In the 2nd example I
don't understand how the dhcp server decides which IP to give to one
of the member of the multinet. I mean how does it decides which
computer will have 192.168.1.2 or 192.168.2.2
Thank you
Erman Ulusoy

Chris Edson said:
Phillip is correct...
See:
http://www.microsoft.com/resources/...ddocs/en-us/sag_DHCP_imp_UsingSuperscopes.asp

Superscopes should only be used where: multiple logical IP networks
exist
on a single physical segment.

In your case, when you set up the vLAN, this results in two physical
segments, since clients on one vLAN cannot ARP for clients on the other
(nor
can they IP broadcast to the other vLAN)... Thus, the superscope should
not
be used in this case.

--
==============================
Chris Edson
(e-mail address removed)

Upcoming Tech Chat !
August 24, 1:00-2:00p Pacific
DHCP: Configuring and Deploying DHCP with Windows Server 2003 Part 2
Join the DHCP test team as we talk about any questions, concerns, or
recommendations you might have for DHCP Server in Windows Server 2003.
Chat Room:
http://communities2.microsoft.com/home/chatroom.aspx?siteid=34000015

Transcript of previous chat:
http://www.microsoft.com/technet/community/chats/trans/network/net1120.mspx

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================


That doesn't mean you should keep the Superscope. If you have more than
one
subnet in the Superscope,...it is only a matter of time before one of
the
clients gets an address from the wrong subnet and gets cut off on the
network.

Superscopes take everything listed in them and makes them act as one
large
single scope. You need to think that through to its logical conclusion.


--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


We've added the relase the lease on shutdown option. Without changing
the superscope it seems working.

"Phillip Windell" <@.> wrote in message
Click to expand...
Hello Dusty thanks for your answer.
We are using 1 scope for each vlan but they are all under a
superscope. I've found in some of the newsgroups post that this
could

Superscopes are used to make multiple ranges behave as a single
range. That
is not what it sounds like you want. Do not use Superscopes,...just
use
*normal* individual Scopes for each "subnet".
Click to expand...
Click to expand...
Click to expand...
 
erman said:
In this 2nd example of superscope it seems to be that the 192.168.1.11
computer won't be able to connect to other computers as the subnet
mask is 255.255.255.0
Click to expand...

Don't use Superscopes. Use separate *normal* Scopes for each subnet. One
scope per subnet.
(the computers with 192.168.2 and 192.168.3) When I define 3 scopes
with 192.168.1 , 192.168.2 , 192.168.3 how the dhcp server decides
Click to expand...

The router is to be configured to forward DHCP request from the clients to
the DHCP Server. Typically this targets a specific DHCP Server although some
may just dump the requests onto a target subnet where the DHCP Server lives.
The packets from the router contain the information the DHCP Server needs to
be able to determine the proper Scope to draw the address from to fill the
request.
I mean isn't it a network with 3 groups of computers where neither of
the groups see the other one?
Click to expand...

No, it is three groups that don't "broadcast" to each other. Routers stop
broadcasts. "Seeing each other" is a non-specific, almost mystical term
anymore, that could mean about anything. Networking is too complex to use
that to describe connectivity, although people do that all the time.
 
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